# π₀ (pi0)

This repository contains the Hugging Face port of **π₀**, adapted from [OpenPI](https://github.com/Physical-Intelligence/openpi) by the Physical Intelligence.
It is designed as a **Vision-Language-Action model for general robot control**.

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## Model Overview

| Feature              | π₀                                                     | π₀.₅                                      |
| -------------------- | ------------------------------------------------------ | ----------------------------------------- |
| Time Conditioning    | Concatenates time with actions via `action_time_mlp_*` | Uses `time_mlp_*` for AdaRMS conditioning |
| AdaRMS               | Not used                                               | Used in action expert                     |
| Tokenizer Length     | 48 tokens                                              | 200 tokens                                |
| Discrete State Input | False (Uses `state_proj` layer)                        | True                                      |
| Parameter Count      | Higher (includes state embedding)                      | Lower (no state embedding)                |

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## Citation

If you use this work, please cite both **OpenPI** and the π₀ paper:

```bibtex
@misc{openpi2024,
  author       = {Physical Intelligence Lab},
  title        = {OpenPI: PyTorch Implementation of π0 and π0.5 Policies},
  year         = {2024},
  publisher    = {GitHub},
  howpublished = {\url{https://github.com/Physical-Intelligence/openpi}},
  license      = {Apache-2.0}
}

@misc{black2024pi0visionlanguageactionflowmodel,
  title        = {π₀: A Vision-Language-Action Flow Model for General Robot Control},
  author       = {Kevin Black and Noah Brown and Danny Driess and Adnan Esmail and Michael Equi and Chelsea Finn and Niccolo Fusai and Lachy Groom and Karol Hausman and Brian Ichter and Szymon Jakubczak and Tim Jones and Liyiming Ke and Sergey Levine and Adrian Li-Bell and Mohith Mothukuri and Suraj Nair and Karl Pertsch and Lucy Xiaoyang Shi and James Tanner and Quan Vuong and Anna Walling and Haohuan Wang and Ury Zhilinsky},
  year         = {2024},
  eprint       = {2410.24164},
  archivePrefix= {arXiv},
  primaryClass = {cs.LG},
  url          = {https://arxiv.org/abs/2410.24164},
}
```

---

## License

This port follows the **Apache 2.0 License**, consistent with the original [OpenPI repository](https://github.com/Physical-Intelligence/openpi).
